Such nano-turbine should also have the application in rheology measurement. Our results exhibit the stable linear dependence of rotation rate on the flow velocity, suggesting the nano-turbine can reliably reflect the flow velocity in various environments. The ratio of the standard deviation to the mean value of rotation period decreases as the flow velocity increases and the relationship between them can be fit to the reciprocal of square root function very well. On the other hands, the nano-turbine is found to rotate back-and-forth in small time period (less than 1 ns), but moves forward in the long run. Meanwhile, such linear relationship remains intact at different temperatures. the water slippage and dragging, may get enhanced at the same time. One possible explanation of the robust linear relationship between the rotation rate and flow velocity is that the other impacts, e.g.
It is interesting to note that the ratio of effective driving flow velocity decreases as the flow velocity increase, suggesting that the linear relationship between rotation rate and flow velocity may be more complicated. The disruption of water flow, together with the water slippage at graphene surface and the dragging effect, should be related to the much slower rotation rate. As indicated by the distribution of flow velocity, the “effective” driving flow velocity is remarkably smaller than the bulk flow velocity and the ratio can be as low as 0.15. Its efficiency of converting energy from fluid flow to the mechanical motion is only 6.4% of that of an ideal macroscopic counterpart. Compared to the macroscopic counterpart, the rotation rate of nano-turbine is much slower. We found the averaged rotation rate of the nano-turbine shows linear relationship with the flow velocity through two orders of magnitude. On the basis of the simulation of this designed model system, the rotation behavior of nano-turbine and the corresponding mechanism is studied in this work. Despite many great progresses achieved in the development of nano-devices, the mechanism by which the nano-device works at nanoscale and the difference between the behavior of mechanical motion of a nano-device and its macroscopic analogue still largely remain elusive 22. This nano-turbine can largely unidirectionally rotate as driven by a steady water flow. Here we present a designed nano-turbine constructed by a single-wall carbon nanotube (CNT) and graphene sheets.
Even though the fluid flow is very relevant and available, the design of nano-turbine that can be driven by fluid flow is still a challenge 21 and there are limited theoretical studies about the rotational behavior of flow-driven nano-turbine. There are many theoretical and experimental attempts to develop the nanomachine that can induce directional rotation as driven by electric or optical field 16, 17, 18, 19, 20. With the development of modern nanotechnology, it becomes possible to design and construct functional artificial nanoscopic devices, resembling shuttles 8, 9, turnstiles 10, cars 11, 12, scissors 13, ratchets 14 and muscles 15. Among the most important functions of these motor proteins is to generate the rotational motion, e.g. There are many nanoscopic machines in biological systems 1, 2, 3, 4, 5, 6, 7. These findings may serve as a foundation for the further development of rotary nano-devices and should also be helpful for a better understanding of the biological molecular motors. Moreover, counterintuitively, the ratio of “effective” driving flow velocity increases as the flow velocity increases, suggesting that the linear dependence on the flow velocity can be more complicated in nature. This discrepancy is shown to be related to the disruption of water flow at nanoscale, together with the water slippage at graphene surface and the so-called “dragging effect”. More interestingly, a striking difference from its macroscopic counterpart is identified: the rotation rate is much smaller (by a factor of ~15) than that of the macroscopic turbine with the same driving flow.
A robust linear relationship is achieved with this nano-turbine between its rotation rate and the fluid flow velocity spanning two orders of magnitude and this linear relationship remains intact at various temperatures. Rotation motion of nano-turbine is quantitatively studied by molecular dynamics simulations on this model system. Here, we design a nano-turbine composed of carbon nanotube and graphene nanoblades, which can be driven by fluid flow. Construction of nano-devices that can generate controllable unidirectional rotation is an important part of nanotechnology.
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